I would suggest a Sony A7S ii or iii... The ii only does 1080p video the iii will also do 4k. Either one of them is very good for low light as that is what they were really designed for. If you want better photo but are willing to give up a bit on the video then an A7iii is a good option.
Now all that said, you do realize that chasing good low light photos is going to cost you good amount of cash to achieve. I have wasted a consider amount of my vacation time and money chasing low light photos at Disney over the years, using ultra fast lens and the reality at the end of it all is I just ask myself why did I bother? It was a bit like trying to catch a large mouth bass... You can do it, but most people you know don't care. Even in my family my wife thinks its silly as she see no point in trying to get photos of ride whether dark or light. My kids don't care with the youngest usually mentioning some youtube video she saw of the same thing. In fact the last time we did WDW I didn't bother taking anything other than a decent point and shoot. I didn't try to shoot any low light rides, I just decided to enjoy the moment with my family and rely on my memories instead of fiddling with cameras and lenses in the hope of capturing a perfect low light shot.
So before you spend several thousand dollars on cameras and lenses, ask yourself if it is really going to be worth it. If it is, then the real key is in the camera not the lens. I can promise you that spending lots of money on lenses that are f1.2 or faster doesn't help. The depth of field is simply too shallow for you to get a decent photo or video with those lenses unless you stop down to about 1.8 at which point what was the purpose of buying the super fast lens? So remember that and it'll save you a couple thousand.
